In a small saucepan, combine soy sauce, mirin, honey, rice vinegar, sesame oil, minced garlic, and grated ginger. Bring to a gentle simmer over medium heat, 2–3 minutes.
Whisk the cornstarch slurry and slowly add it to the simmering sauce. Stir until the sauce thickens and coats the back of a spoon, about 1 minute. Remove from heat and reserve 2 tablespoons for serving.
Pat the fillets dry and season lightly with salt and pepper. Arrange fillets skin-side down on a parchment-lined baking sheet or greased baking dish.
Brush each fillet with the glaze, keeping a bit back for serving. Preheat oven to 400°F (200°C) and bake for about 10–12 minutes, until the salmon flakes easily and reaches 125–130°F for medium doneness.
For a caramelized top, broil on high for 1–2 minutes, watching carefully so the glaze doesn’t burn.
Drizzle reserved glaze, sprinkle sesame seeds and scallions, and serve with lemon or lime wedges over rice or salad.
Notes
To marinate, toss fillets with half the glaze for up to 1 hour to add flavor, but avoid longer to prevent the acid from firming the fish.
Adjust sweetness by adding more or less honey or brown sugar.
Reheat leftover salmon gently in a 300°F oven for 8–10 minutes to avoid drying it out.